Pielke Senior on the Borenstein AP statistics article

Comments On AP Story “Statistics Experts Reject Global Cooling Claims”

There is a news report titled “Statistics experts reject global cooling claims” by Seth Borenstein which appeared today.

The article reads

“WASHINGTON — The Earth is still warming, not cooling as some global warming skeptics are claiming, according to an analysis of global temperatures by independent statistics experts.

The review of years of temperature data was conducted at the request of The Associated Press. Talk of a cooling trend has been spreading on the Internet, fueled by some news reports, a new book and temperatures that have been cooler in a few recent years.

The statisticians, reviewing two sets of temperature data, found no trend of falling temperatures over time. And U.S. government figures show that the decade that ends in December will be the warmest in 130 years of record-keeping.

Global warming skeptics are basing their claims on an unusually hot year in 1998. They say that since then, temperatures have fallen — thus, a cooling trend. But it’s not that simple.

Since 1998, temperatures have dipped, soared, dropped again and are now rising once more. Records kept by the British meteorological office and satellite data used by climate skeptics still show 1998 as the hottest year. However, data from the U.S. National Oceanic and Atmospheric Administration and NASA show 2005 has topped 1998.

“The last 10 years are the warmest 10-year period of the modern record,” said NOAA climate monitoring chief Deke Arndt. “Even if you analyze the trend during that 10 years, the trend is actually positive, which means warming.”

Statisticians said the ups and downs during the last decade repeat random variability in data as far back as 1880.”

This article, however, (which is not a true independent assessment if the study was completed by NOAA scientists)  is not based on the much more robust metric assessment of global warming as diagnosed by upper ocean heat content. Nor does it consider the warm bias issues with respect to surface land temperatures that we have raised in our peer reviewed papers; e.g. see and see.

With respect to ocean heat content changes, as summarized in the articles

Ellis et al. 1978: The annual variation in the global heat balance of the Earth. J. Climate. 83, 1958-1962.

Pielke Sr., R.A., 2003: Heat storage within the Earth system. Bull. Amer. Meteor. Soc., 84, 331-335

Pielke Sr., R.A., 2008: A broader view of the role of humans in the climate system. Physics Today, 61, Vol. 11, 54-55

and

Douglass, D.H. and R. Knox, 2009: Ocean heat content and Earth’s radiation imbalance. Physics letters A

trends and anomolies in the upper ocean heat content permit a quantitative assessment of the radiative imbalance of the climate system.

Jim Hansen agrees on the use of the upper ocean heat content as an important diagnostic of global warming.   Jim Hansen in 2005 discussed this subject (see). In Jim’s write-up, he stated

“The Willis et al. measured heat storage of 0.62 W/m2 refers to the decadal mean for the upper 750 m of the ocean. Our simulated 1993-2003 heat storage rate was 0.6 W/m2 in the upper 750 m of the ocean. The decadal mean planetary energy imbalance, 0.75 W/m2, includes heat storage in the deeper ocean and energy used to melt ice and warm the air and land. 0.85 W/m2 is the imbalance at the end of the decade.

Certainly the energy imbalance is less in earlier years, even negative, especially in years following large volcanic eruptions. Our analysis focused on the past decade because: (1) this is the period when it was predicted that, in the absence of a large volcanic eruption, the increasing greenhouse effect would cause the planetary energy imbalance and ocean heat storage to rise above the level of natural variability (Hansen et al., 1997), and (2) improved ocean temperature measurements and precise satellite altimetry yield an uncertainty in the ocean heat storage, ~15% of the observed value, smaller than that of earlier times when unsampled regions of the ocean created larger uncertainty.”

As discussed on my weblog and elsewhere (e.g. see and see), the upper ocean heat content trend, as evaluated by its heat anomalies, has been essentially flat since mid 2003 through at least June of this year.  Since mid 2003, the heat storage rate, rather then being 0.6 W/m2 in the upper 750m that was found prior to that time (1993-2003), has been essentially zero.

Nonetheless, the article is correct that the climate system has not cooled even in the last 6 years. Moreover, on the long time period back to 1880, the consensus is that the climate system has warmed on the longest time period. Perhaps the current absence of warming is a shorter term natural feature of the climate system.  However, to state that the “[t]he Earth is still warming” is in error. The warming has, at least temporarily halted.

The article (and apparently the NOAA study itself), therefore, suffers from a significant oversight since it does not comment on an update of the same upper ocean heat content data that Jim Hansen has used to assess global warming.